A Field of the Invention
The present invention relates to a thin film transistor array panel, and in particular, a thin film transistor array panel including a fan-out area provided with connections for connecting a wire and a pad between a display area and the pad area.
B Description of Related Art
A thin film transistor (TFT) array panel is used as a circuit panel for independently driving pixels of a display device such as an LCD and an organic electroluminescence (EL) display device. The TFT array panel includes a scanning signal wire or a gate wire transmitting scanning signals and an image wire a data wire transmitting data signals, a plurality of TFTs connected to the gate wire and the data wire, a plurality of pixel electrodes connected to the TFTs, the gate insulating layer covering and insulating the gate wire, and a passivation layer covering and insulating the TFTs and the data wire. The TFTs include the gate electrodes, which are portions of the gate wire, a semiconductor layer forming channels, the source electrodes and the drain electrodes, which are portions of the data wire, the gate insulating layer, the passivation layer, and so on. The TFTs are switching elements for transmitting and blocking the data signals to be supplied to the pixel electrodes from the data wire in response to the scanning signals from the gate wire.
A plurality of driving ICs for applying driving signals to gate lines and data lines are connected to the TFT array panel. The driving ICs are connected to the gate lines and the data lines through a plurality of pads, and the pads are gathered in narrow areas for connection to the driving ICs. On the contrary, the distances between the gate lines or the data lines on a display area, which are determined by the size of pixels, are larger than the distances between the pads. Accordingly, there are a plurality of areas between pad areas and the display area, where the distances of the signal lines increases, and the areas are called fan-out areas. The existence of the fan-out areas results in the difference in the length between the signal lines, and thus the difference in the RC delay between the signal lines. The difference of the RC delay differentiates images to deteriorate image quality.
The fan-out area occupies a narrow area and is located between the display area provided with a plurality of pixels and edges of the panels. When a common bar connecting a plurality of storage electrode lines and applying a common voltage to the storage electrode lines are disposed between the display area and the pad areas, the common bar occupies a portion of the areas to be assigned to the fan-out areas. As the fan-out areas are narrower, the curved angles of the signal lines in the fan-out areas are larger to increase the difference in the length between the signals lines and the width of the signal lines is smaller. Accordingly, the difference in the resistance between the signal lines on the fan-out areas is amplified.
This problem is much severe for a COG (chip on glass) type LCD. The pitch, i.e., the distance between output pins of a COG chip is about 45 microns, which is very small compared with the pitch of 100 microns between output pads in TAB (tape automatic bonding) type. Therefore, the curved angles of the signal may be much increased.